š Op-Amp Configurations
Calculate gain, output voltage, and resistor values for common op-amp circuits.
Non-Inverting Amplifier
$$V_\text{out} = V_\text{in} \times \left(1 + \dfrac{R_f}{R_1}\right)$$
ā Please enter valid values.
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š” Minimum gain is +1 V/V . The (+) input connects to Vin ; R1 goes from (ā) to GND; Rf feeds back from output to (ā).
Inverting Amplifier
$$V_\text{out} = -V_\text{in} \times \dfrac{R_f}{R_\text{in}}$$
ā Please enter valid values.
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š” Output is phase-inverted. The (+) input is tied to GND (or a bias voltage). The bias resistor Rbias = Rin ā Rf minimises offset errors.
Summing Amplifier (Inverting)
$$V_\text{out} = -R_f\!\left(\dfrac{V_1}{R_1}+\dfrac{V_2}{R_2}+\dfrac{V_3}{R_3}\right)$$
Input channels (leave unused channels blank):
ā Please enter Rf and at least one complete V/R pair.
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š” If all input resistors are equal to Rf , the output equals the inverted sum of inputs: Vout = ā(V1 + V2 + ā¦).
Differential Amplifier
$$V_\text{out} = \dfrac{R_f}{R_1}\,(V_2 - V_1)$$
ā Please enter valid values.
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š” Requires matched resistors (R1 = R3 and Rf = R4 ) for good common-mode rejection. CMR degrades with resistor tolerance mismatch.
Voltage Follower (Unity-Gain Buffer)
$$V_\text{out} = V_\text{in} \qquad \text{Gain} = +1\,\text{V/V}\;(0\,\text{dB})$$
ā Please enter a valid input voltage.
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š” No external resistors needed. Output tracks input with very high input impedance and very low output impedance ā ideal for impedance buffering between stages.